FRF- Phase difference

[Petar2015]

Hi,

I have acquired the input and output of my DUT. Both of them are as time-wave (Voltage).

The input is from a function generator, and the output from a photodiode.

Now I want to obtaine the FRF and phase difference vetween these two waves, Does anyone know how can I do that?

Also, I have performed the sweep by the Function generator, too. so the input is Swept-freq.

I have attached the project (Sound and vibration toolkit)

Thanks

Petar

[dsb@NI]

For each bin frequency the Frequency Response Step returns the magnitude and phase of the response signal / stimulus signal. Your project already had this step. Only the data saved as a log in the project was available for us to look at. Using a Power Spectrum Step, it appears that you configured your sweep to output a signal from 10 Hz to 100 Hz, so that is the region of the FRF that we should examine. Because you are using a sweep, change the window in the Frequency Response Step to None.

You may want to perform a longer sweep to improve frequency resolution and/or average several sweeps to maximize signal-to-noise ratio.

[Petar2015]

Hi

Thanks for your reply, I really appreciate it. Actually it has been a while that like I got stuck in this problem.

So, if I understood your reply correctly, The only solution would be, to increase the sweep range, for example instead of 100 to 2kHz.

But about the "averaging", Could you please give me a heads up, I'm new user sooooo.. 😞

And, when I check the "Coherence" in the Freq-Response step, the coherence is Zero....every where, Do you know what could be the reason?

Thanks

Petar